psql: Make ParseVariableDouble reject values above max

psql: Make ParseVariableDouble reject values above max

ParseVariableDouble missed returning false after logging an error when
the parsed value exceeded max, making the value assigned rather than
rejected.  Backpatch down to v18 where this was introduced as part of
the \WATCH_INTERVAL.

Author: Sven Klemm <sven@tigerdata.com>
Co-authored-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Discussion: https://postgr.es/m/CAMCrgp31p_5SDVi7dwnP39tTW5icQ0MWHA+N4kJdXgkL0PEy8w@mail.gmail.com
Backpatch-through: 18